1. Field of the Invention
This application relates to novel protein tyrosine kinases, the nucleic acid sequences encoding these proteins, the extracellular domains of the proteins, ligands to the protein tyrosine kinases, antibodies specific for the encoded proteins and methods of use therefor. In particular, this application relates to the novel receptor protein tyrosine kinases designated Rse and HPTK6.
2. Description of Related Art
Intracellular signals which control cell growth and differentiation are often mediated by tyrosine kinase proteins. Tyrosine kinases catalyze protein phosphorylation using tyrosine as a substrate for phosphorylation. Members of the tyrosine kinase family can be recognized by the presence of several conserved amino acid regions in the tyrosine kinase catalytic domain (Hanks et al., Science: 241: 42-52 [1988]). The tyrosine kinase domain is crucial for the signal transduction pathways required for mitogenesis, transformation and cell differentiation. Certain tyrosine kinases predominantly stimulate cell growth and differentiation, whereas other tyrosine kinases arrest growth and promote differentiation. Furthermore, depending on the cellular environment in which it is expressed, the same tyrosine kinase may either stimulate, or inhibit, cell proliferation (Schlessinger et al., Neuron, 9: 383-391 [1992]).
Tyrosine kinase proteins can be classified as either receptor tyrosine kinases or intracellular tyrosine kinases. Receptor tyrosine kinases (rPTKs) convey extracellular signals to intracellular signaling pathways thereby controlling cell proliferation and differentiation. These rPTKs share a similar architecture, with an intracellular catalytic portion, a transmembrane domain and an extracellular ligand-binding domain. (Schesslinger et al., supra). The extracellular domains (ECDs), which are responsible for ligand binding and transmission of biological signals, have been shown to be composed of a number of distinct structural motifs. The intracellular domain comprises a catalytic protein tyrosine kinase. The binding of ligand to the extracellular portion is believed to promote dimerization of the rPTK resulting in transphosphorylation and activation of the intracellular tyrosine kinase domain. In addition to their catalytic function, the intracellular domains (ICDs) of rPTKs may also serve as binding sites for other components of the signal transduction pathway. In particular, some proteins containing src-homology 2 (SH2) domains have been shown to interact in a phosphorylation-dependent and sequence specific manner to specific tyrosine residues within the ICD (Cantley et al., Cell, 64: 281-302 [1991]).
A large number of protein tyrosine kinases have been characterized on the basis of their amino acid and nucleic acid sequences. For a review of these proteins see Hanks et al., supra.
WO 93/15201 discloses isolation of several novel rPTK genes found in human megakaryocytic and lymphocytic cells using degenerate oligonucleotide probes as primers in a polymerase chain reaction (PCR) to amplify tyrosine kinase DNA segments.
The recent publication by Johnson et al., Proc. Natl. Acad. Sci., 90: 5677-5681 (1993) discusses the characterization of a receptor tyrosine kinase called discoidin domain receptor (i.e., DDR) which is abundantly expressed in breast carcinoma cell lines. DDR is considered to have two features not found in other receptor tyrosine kinases. First, a region of the amino acid sequence near the N terminus of DDR contains a "discoidin I-like domain". This determination was based on the sequence identity between this region and the protein, discoidin I (see FIG. 5 of Johnson et al.). Discoidin I-like domains are present as tandem repeats at the C terminus of the light chains of factor V (Kane, W. H. & Davie, E. W., Proc. Natl. Acad. Sci., 83: 6800-6804 [1986]), factor VIII (Toole et al., Nature(London), 312: 342-347 [1984]) and Vehar et al., Nature(London), 312: 337-342 [1984], and two milk fat globule membrane proteins, MFG.E8 (see Stubbs et al., Proc. Natl. Acad. Sci., 87: 8417-8421 [1991]) and BA46 (see Larocca et al., Cancer Res., 51: 4994-4998 [1991]). Second, the DDR protein has an extensive proline/glycine-rich region between the discoidin I-like domain and the transmembrane domain and another such region between the transmembrane domain and the C-terminal tyrosine kinase domain. These proline/glycine-rich regions are not found in other receptor protein tyrosine kinases. The catalytic domain of DDR shares 45% sequence identity with the trk protein catalytic domain disclosed in Martin-Zanca et al., Mol. Cell. Biol., 9:24-33 (1989). Zerlin et al. disclose isolation of the murine equivalent of the DDR rPTK found by Johnson et al., which they call NEP (Oncogene,8: 2731-2939 [1993]).
WO 92/14748 discloses a receptor, designated KDR, which is classified as a type III receptor tyrosine kinase and binds to vascular endothelial cell growth factor. The type III group of rPTKs includes the c-kit proto-oncogene and the receptors for platelet derived growth factor (PDGF) and colony stimulating factor-1 (CSF-1).
Matthews et al., Proc. Natl. Acad. Sci., 88: 9026-9030 (1991) refer to the isolation of rPTK clone from a population of hematopoietic murine cells which, like KDR, exhibits a close sequence identity to c-kit. This receptor is called flk-1. The flk-1 receptor was isolated using an anti-sense oligonucleotide primer and anchored PCR. Chromosomal mapping indicated that the flk-1, kit and pdgfra genes are closely linked. Matthews et al., Cell, 65: 1143-1152 (1991) discuss isolation of a rPTK called flk-2, from stem cell-enriched murine hematopoietic tissue. U.S. Pat. No. 5,185,438 also refers to the rPTKs, flk-1 and flk-2, which are said to be expressed in primitive hematopoietic cells but not in mature hematopoietic cells.
Lai et al., Neuron, 6: 691-704 (1991) used PCR to identify several cDNAs encoding part of the tyrosine kinase domains of various rat rPTKs. The newly isolated sequences were designated tyro-1 to tyro-13. Because preferential expression of several of the sequences in the developing vertebrate nervous system was evidenced, Lai et al. concluded that protein-tyrosine kinases appear to play a central role in neural development.
Holtrich et al., Proc. Natl. Acad. Sci., 88:10411-10415 (1991) studied the expression of protein-tyrosine kinases in normal human lung and tumor cells by PCR followed by molecular cloning and sequence analysis. Six known PTKs (yes, fgr, lyn, hck, pdgfb-r and csfl-r) were detected as well as two new PTKs. One of the proteins detected appeared to be cytosolic. The other PTK, designated TKF, was found to be related to fibroblast growth factor receptor and was only found expressed in the lung.
WO 93/14124 discloses the cloning, sequencing and expression of a human rPTK termed tie which is expressed in cultured endothelial cells as well as tumor cell lines. The extracellular domain (ECD) of tie was found to contain stretches of amino acid sequence having features of the immunoglobulin, epidermal growth factor and fibronectin type III repeat protein families.
Partanen et al., Proc. Natl. Acad. Sci., 87: 8913-8917 (1990) analyzed PCR amplified cDNA clones which lead to the identification of 14 different tyrosine kinase-related sequences, designated JTK1-14. Based on the pattern of expression of the clones, it was suggested that the tyrosine kinases encoded by the complete sequences most probably play a role in the differentiation of megakaryoblasts or in the physiology of platelets.
While Partanen et al. discuss isolation of the partial JTK11 cDNA clone, the later publication by Janssen et al., Oncogene, 6: 2113-2120 (1991), reports the cDNA cloning of the entire oncogene (designated UFO) encoding a 894 amino acid polypeptide. Janssen et al. identified the UFO tyrosine kinase receptor by DNA transfection analysis of bone marrow cells from a patient suffering from a chronic myeloproliferative disorder. It is noted in this publication that several oncogene products are rPTKs, e.g. colony-stimulating factor-1 and TRK. Around the same time that Janssen et al. isolated the rPTK they call UFO, O'Bryan et al. isolated the same rPTK (which they designate Axl) from human myeloid leukemia cells (O'Bryan et al., Mol. Cell. Biol., 11: 5016-5031 [1991]). Axl is a transforming gene which encodes a rPTK having two fibronectin type III repeats and two immunoglobulin-like repeats in the extracellular domain thereof. These motifs are also found in the extracellular domain of the receptor-like protein tyrosine phosphatase, PTP.mu. (Brady-Kalnay et al., J. Cell Biol., 122: 961-972 [1993]). The immunoglobulin domain and four fibronectin type-III repeats of PTP.mu. are similar to the motifs found in cell-cell adhesion molecules. Brady-Kalnay et al. propose that the ligand for the PTP.mu. may be another PTP.mu. on an adjacent cell.
Faust et al., Oncogene, 7: 1287-1293 (1992) disclose cloning of the mouse homologue of the UFO oncogene identified in the publication by Janssen et al. This murine tyrosine kinase has an overall sequence identity of 87.6% with the human sequence. The extracellular domain of the UFO receptor is characterized by the existence of two immunoglobulin-like (IgL) and two fibronectin type III (FNIII) repeats. As discussed in Faust et al., a combination of IgL and FNIII domains are also found in several neural cell adhesion molecules and receptor tyrosine phosphatases suggesting that these structures are important for intercellular communication.
Wilks et al., Gene, 85: 67-74 (1989) used degenerate oligo-deoxyribonucleotide (oligo) primers derived from amino acid sequence motifs held in common between all members of the PTK family to prime the amplification of PTK sequences. It was found that the most effective type of primer for identification of PTK sequences is a short, moderately degenerate, oligo primer. Using the techniques disclosed, Wilks and his co-workers isolated a new mammalian PTK sequence as well as other known PTK sequences.
Brauninger et al., Gene, 110(2): 205-211 (1992) disclose isolation of a human gene encoding an intracellular protein belonging to a new subclass of protein tyrosine kinases. The clone, designated csk, was found to be expressed in human lung and macrophages. The csk gene was distinguished from the src family of proto-oncogenes by the lack of certain tyrosine autophosphorylation sites in the amino acid sequence and the lack of a N-terminal myristylation site.
It is evident that a number of rPTKs are involved in cell growth and differentiation, many of which have been characterized to date.
Additional rPTKs are needed in order to further study growth and differentiation of cells, for use as therapeutic agents and for diagnostic use.
Accordingly, it is an object of this invention to identify and purify one or more novel protein tyrosine kinase receptors. It is yet another object to provide derivatives and modified forms of such new polypeptides, including amino acid sequence variants and covalent derivatives thereof.
It is another object to provide nucleic acid encoding such novel rPTKs and to use this nucleic acid to produce rPTKs in recombinant cell culture. The rPTK protein thus produced can be used for investigational, therapeutic or diagnostic use. Nucleic acid sequences which hybridize with the DNA or RNA encoding the proteins described herein can also be used as anti-sense oligonucleotides to inhibit protein tyrosine kinase activity either in vivo or in vitro.
It is a further object to provide amino acid sequences encoding the ECDs of the novel rPTKs, which sequences are useful for in vitro assays or for use as therapeutic agents. The ECDs, or variants thereof, can also be used as immunogens for raising antibodies, including agonist antibodies to the rPTKs. Nucleic acid sequences encoding the novel rPTK ECDs are needed in order to make these polypeptides recombinantly.
Ligands to the novel rPTKs are also desirable for use as therapeutic agents to stimulate the receptor and thereby stimulate cell growth and/or differentiation. Such ligands are useful for determining the function and biological activity of the receptors.
These and other objects will be apparent to the ordinary artisan upon consideration of the specification as a whole.